• Tunnel and Underground Space
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• v.24 no.3
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• pp.212-223
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• 2014

In this study, the stability analyses for metal mine roadways at a great depth were performed. In-situ stress measurements using hydrofracturing, numerous laboratory tests for rock cores and GSI & RMR classifications were conducted in order to find the physical properties of both intact rock and in-situ rock mass distributed in the studied metal mine. Through the scenario analysis and probabilistic assessment on the results of rock mass classification, the in-situ ground conditions of mine roadways were divided into the best, the average and the worst cases, respectively. The roadway stabilities corresponding to the respective conditions were assessed by way of the elasto-plastic analysis. In addition, the appropriate roadway shapes and the support patterns were examined through the numerical analyses considering the blast damaged zone around roadway. It was finally shown to be necessary to reduce the radius of roadway roof curvature and/or to install the crown reinforcement in order to enhance the stability of studied mine roadways.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.4 s.334
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• pp.29-36
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• 2005

Many novel designs of planar antennas for related applications such as internal mobile phone antennas, base station antennas, WLAN or Bluetooth antennas, and so on, have been reported very recently, especially since the year 2000. In this thesis, Dualband internal antenna for GSM/DSC handset is proposed. The antenna has a size of about 38mm$\times$90mm$\times$1mm, giving a total mobile phone PCB for support and fold type Patch of about 30mm$\times$8mm$\times$3.2mm. This antenna characteristic facilitates the fine-tuning of the two operating frequencies of 909MHz and 1762MHz in this dualband design. The measured radiation pattern in the E-plane and H-plane for operating frequencies of 909MHz and 1762MHz is compared and analyzed. The designed and fabricated two band internal antenna for GSM/DSC handset have a gain between 0dBi and 2.0dBi at all bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.930-935
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• 2009

This paper describes a miniaturezed metamaterial BT chip antenna for mobile devices. The size of the proposed antenna is $3.0\;mm(W){\times}2.0\;mm(L){\times}1.2\;mm(H)$. And it is fabricated by chip type. The zeroth-order resonant properties are analyzed by magnitude and phase distributions of the surface current using surface current scanning system. The antenna offers omni-directional radiation patterns and measured 3D average gain is over - 1.7 dBi.

• Journal of IKEEE
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• v.14 no.3
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• pp.224-231
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• 2010

Automatic detection of objects in images has been one of core challenges in the areas such as computer vision and pattern analysis. Especially, with the recent deployment of personal mobile devices such as smart phone, such technology is required to be transported to them. Usually, these smart phone users are equipped with devices such as camera, GPS, and gyroscope and provide various services through user-friendly interface. However, the smart phones fail to give excellent performance due to limited system resources. In this paper, we propose a new scheme to improve object recognition performance based on pre-computation and simple local features. In the pre-processing, we first find several representative parts from similar type objects and classify them. In addition, we extract features from each classified part and train them using regression functions. For a given query image, we first find candidate representative parts and compare them with trained information to recognize objects. Through experiments, we have shown that our proposed scheme can achieve resonable performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.955-964
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• 2010

In this paper, a compensation method of the amplitude and phase errors from the T/R(Transmit/Receive) modules in an active SAR(Synthetic Aperture Radar) system is introduced. The errors are defined and classified, and characterized by analyzing the measurement data acquired from the pilot test. To compensate these errors, a control methodology of T/R modules output is proposed. Before the compensation is applied, 16 T/R modules integrated on the active SAR antenna show the amplitude in 28.2~29.0 dBm and the phase in $101.7^{\circ}{\sim}165.2^{\circ}$. After the compensation, the amplitude and phase are distributed in 27.4~28.0 dBm and $116.1^{\circ}{\sim}120.0^{\circ}$ respectively. The antenna beam patterns generated by the array theory with the distributions are compared, and the proposed method is verified as good to apply for the active SAR system.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.230-230
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• 2010

질화갈륨 기반의 III족-질화물 계열의 반도체 물질은 녹색-자외선 영역의 발광다이오드에 응용되어 왔으며 고효율, 고휘도 발광소자의 구현 및 성능 향상을 위해 많은 연구가 진행되었다. 일반적으로 널리 사용되어온 c축 방향으로 성장된 질화갈륨 기반 발광다이오드에서는 활성층의 에너지 밴드구조가 내부전기장에 의해 변형되어 전자와 정공의 재결합 확률이 저하된다. c축 방향으로 형성되는 내부전기장은 축방향으로의 자발적 분극화와 높은 압전 분극 현상에 기인한다. 이와 같은 분극 성장에서의 내부양자효율 저하 현상을 해결하기 위하여 내부 전기장이 존재하지 않는 a축과 m축과 같은 무분극 방향으로의 성장이 집중적으로 연구되고 있다. 현재 사파이어 기판위에서 무분극 성장된 박막은 높은 밀도의 결함이 발생하여 고품위의 발광다이오드 동작에 어려움을 겪고 있다. 최근 결함 밀도를 낮추고 높은 결정성을 갖는 무분극 질화갈륨 박막을 성장하기 위하여 2-단계 성장 방법, 나노구조층 삽입, 산화규소 마스크 패턴 등 다양한 성장 방법들이 연구되어 주목할 만한 연구 결과들이 보고되고 있다. 다양한 성장 방법들에 의해 성장된 박막들은 고유한 특성들을 보이는데, 특히 박막 성장방법에 따라 박막 내부에 형성되는 깊은 준위의 특성들은 발광다이오드의 소자 특성에도 큰 영향을 미치게 되므로 무분극 박막에서의 깊은 준위에 대한 연구가 필요하다. 본 연구에서는 금속-유기 화학기상증착 방법으로 r면의 사파이어기판 위에 a면의 질화갈륨을 성장시켰다. 고품질의 결정성을 구현하기 위해 저온 핵형성층, 3차원 성장층, 2차원 중간온도 성장층, 2차원 성장층의 4개 버퍼층을 사용하였으며, 질화규소 나노구조층을 삽입함으로써 고품 위의 a면 질화갈륨 박막을 구현하였다. 성장된 a면 질화갈륨 박막에 형성된 깊은 준위들은 접합용량과도분광법을 이용하여 분석되었으며 질화규소 삽입층의 유무에 따른 깊은 준위의 특성 차이에 대한 연구를 수행하였다.

• Journal of Wetlands Research
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• v.20 no.2
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• pp.116-123
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• 2018

The objective of this study was to examine effects of stand age on soil $CO_2$ efflux in plantation Pinus koraiensis, and to elucidate what extent plant (fine) root and soil microbial biomass contribute to the whole soil $CO_2$ efflux. In three age classes (20-yr-old. 40-yr-old, 70-yr-old) of plantation Pinus koraiensis, in-situ soil respiration, plant fine root biomass and soil microbial biomass were measured from April to November in 2004. Regardless of stand age, soil temperature and soil $CO_2$ efflux increased until July then slowly decreased. Soil respiration was higher in 70-yr-old stand than in 20- and 40-yr stands. Fine root biomass and soil microbial biomass was also higher in 70-yr-old stand. Root exclusion decreased soil respiration in 40-yr stand, but not in 70-yr stand. Soil microbial biomass was higher in 70-yr stand, but there was no monthly variation between July and November. The results suggest that soil respiration may increase as plant stand ages and microbial contribution could play more roles in older stands.

• Journal of Powder Materials
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• v.21 no.3
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• pp.207-214
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• 2014

In this study, nano-scale copper powders were reduction treated in a hydrogen atmosphere at the relatively high temperature of $350^{\circ}C$ in order to eliminate surface oxide layers, which are the main obstacles for fabricating a nano/ultrafine grained bulk parts from the nano-scale powders. The changes in composition and microstructure before and after the hydrogen reduction treatment were evaluated by analyzing X-ray diffraction (XRD) line profile patterns using the convolutional multiple whole profile (CMWP) procedure. In order to confirm the result from the XRD line profile analysis, transmitted electron microscope observations were performed on the specimen of the hydrogen reduction treated powders fabricated using a focused ion beam process. A quasi-statically compacted specimen from the nano-scale powders was produced and Vickers micro-hardness was measured to verify the potential of the powders as the basis for a bulk nano/ultrafine grained material. Although the bonding between particles and the growth in size of the particles occurred, crystallites retained their nano-scale size evaluated using the XRD results. The hardness results demonstrate the usefulness of the powders for a nano/ultrafine grained material, once a good consolidation of powders is achieved.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.13-23
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• 1998

An intensity of the 1997 Kyungju earthquake(M=4.3) was estimated at three hundred locations based on the field survey and questionaires from 2200 residents. The isoseismal shows almost circular pattern which doesnot reflect some specific geological trends. However,most of the Kyeongsang basin except the southwestern part is included within the area of MM intensity V. There occurred strong shaking, numerous cracks on the wall of the houses, and movement of slate on the roofs, falling of the tiles from the monument. The isoseismal of the highest MM intensity VII, 1-3 km in width and 9 km in length, is elongated along the Yangsan fault, which is located about 1.5 km west from epicenter. The lineaments near the epicenter exhibit almost N-S and NNE directions. The lineament distribution, the pattern of damage area and the solution of fault plane suggest that the Kyongju earthquake occurred with strike-slip sense along the Yangsan fault. The calculated intensity attenuation(I) with distance(R) is as follows : $I{\;}={\;}I_o{\;}+{\;}0.3461{\;}-{\;}0.3274{\;}{\times}{\;}1nR{\;}-{\;}0.086{\;}{\times}{\;}R$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.855-862
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• 2003

This paper suggests the PIFA structure modified antenna in which short-circuit plate is located between planar element and ground plane, in order to solve the problem of narrow band of existing internal antenna, PIFA. It is also suggested that internal antenna has the perturbation in the patch to broaden the frequency bandwidth. It is possible that the antenna is installed into the mobile telephone with a low profile condition(h=0.015 λ) to use internally, and acquired desired bandwidth(5.2 %) through double resonance structure, remodeling the PIFA that is already well-known as an internal antenna. This paper investigated how characteristic is affected by the feeding point(Yf, Zf), short strip plate(Zs), short strip width(Ws), perturbation width(w), length(d), short plate height(h), dielectric($\varepsilon$$\_$r/) to be slim type antenna. It is compared with existing PIFA bandwidth, and is suggested pattern as the H.E plane. It is simulated using the Microwave Studio of the CST Inc. based on FIM(Finite Integration Method) method and analyzed antenna characteristic following the variation each parameters. The result proved the practical use of PIFA antenna by comparing the measured and simulated data of the antenna.